I'm working on putting together something along the lines of a timeline pattern, where a glider flies past a series of year labels, and things that were discovered in various years can be found in some kind of rough order along the glider's path.

I just got to 1991 and found 44P5H2V0, and looking at it I'm a little surprised that no responses have showed up since that last post, with starting points for a synthesis at least. The only thing along those lines that I can find is A for Awesome's comment from several years back, with a pair of MWSSes plus chunks of active reaction at the front. Did anyone give this a try?

The front end looks suspiciously like a pair of B-heptominos halfway evolved into Herschels -- not that I really know what I'm talking about or anything.

dvgrn wrote:I'm working on putting together something along the lines of a timeline pattern, where a glider flies past a series of year labels, and things that were discovered in various years can be found in some kind of rough order along the glider's path.

I just got to 1991 and found 44P5H2V0, and looking at it I'm a little surprised that no responses have showed up since that last post, with starting points for a synthesis at least. The only thing along those lines that I can find is A for Awesome's comment from several years back, with a pair of MWSSes plus chunks of active reaction at the front. Did anyone give this a try?

The front end looks suspiciously like a pair of B-heptominos halfway evolved into Herschels -- not that I really know what I'm talking about or anything.

After a few tries on 44P5H2V0, I thought I'd elaborate on this a little--it's simply a tough nut to crack. My method for a spaceship synthesis is to find a predecessor where the cell transitions are on the outside of the spaceship, with a preference for deaths by overpopulation rather than underpopulation. A for Awesome's near-miss looks good, but there are a pair of wrong cells in the heart of the ship, which can't be salvaged without abandoning the MWSS approach.

Here's my best attempt at a good-looking predecessor, but it doesn't get the not-quite-a-spark wings (see generation 2) correct. I don't know how to fix that myself, but if it's doable, it can be done by making adjustments to the outside of the predecessor rather than its innards, which is exactly what you want for a glider synthesis.

Obviously there's not enough room for everything to fit, but I find that the key to this sort of glider synthesis is to rejigger things over and over again until they do fit.

I had a go at this myself, but the most difficult part seems to be inserting the glider + Z tetronimo. Is anyone else able to complete this synthesis (or get close to), or would a different approach be in order?

Minimum repeat time is currently 690 ticks. Quite possibly that could be reduced somewhat by re-ordering the stages, but 690 is such an auspicious number already that maybe there's no point trying to improve it... That is, it's auspicious if anyone is still so old-fashioned as to want to build a 46P4H1V0 gun with a separate gun for each of the 100 gliders, instead of a nice modern glider-to-46P4H1V0 converter.

I would respectfully encourage anyone creating incremental syntheses of things like this to pick a spacing between intermediate constructions, and stick with it. Getting chris_c's script to work on the synthesis as originally published was a form of cruel and unusual punishment that is specifically forbidden by three different articles of the Geneva Conventions.

77topaz wrote:The 35-glider synthesis would a) be exponentially large and b) we only have a vague idea of what it would actually look like.

True enough. We know exactly what the initial RCT synthesis will look like, except for the detail of exactly how ridiculously far apart we have to move those gliders, so that those collisions happen at the right places to make a clean 46P4H1V0 synthesis.

But we don't really know, for example, what the Cordership fleets will look like that clean up after the block-laying switch engine or the glider-producing ones -- and that's clearly an important part of the 35-glider synthesis of a 46P4H1V0.

I vaguely suspect that swapping things around to do all the construction on one side, then all the construction on the other side, might gain a few more ticks. But I'm not sure why I think that, and not highly motivated to test out the theory.

If anyone wants to try it, just copy the incremental synthesis from the above pattern to a new Golly universe, adjust the stages you want to swap around, and then try running chris_c's script. The only weird thing you'll need to know is that the script won't work unless you select the whole incremental synthesis, plus about 25 empty cells to the left of the first stage. And the separation between stages is 60 cells.

Down to repeat time 614 with the same 99 gliders. I'm still letting the script do all the work, so there might well be cleverer optimizations that would be obvious if someone took a close look at the build order again. All I did was re-order the construction stages as I suggested above, and break apart a couple of stages that were really two stages each, and then re-run chris_c's script.

Separation between stages is now 64, thanks to an adjustment by gmc_nxtman that didn't get mentioned (but things didn't work too well when I started moving stages around with 60-cell jumps.)

<speculative-tangent type="wild">Has anyone done any brute-force searches using the 3-glider recipe list from 2718281828? Basically, rewind each glider recipe by 50 ticks or so, place a "still life of interest" in every possible position in say a 20x20 area centered on the gliders' bounding box, run each collision, and see if some key defined part of the still life is still there and yet the structure has been modified in some way. Maybe "modified" just means that a getcluster() function returns a different list of cells.

Throw all the successful modifications into a big stamp collection and scan through it manually, and it seems like some new stuff might turn up. What got me thinking along these lines was the idea that nine gliders to add five cells, or fourteen gliders to add six cells, might turn out to be suboptimal somehow:

Of course the odds are probably pretty low that a 3-glider collision will solve this particular conversion, but something else interesting might turn up instead...!</speculative-tangent>

EDIT: Finally got sufficiently fed up with having to guess how much empty space to select to the left of the incremental synthesis. Here's a version of chris_c's script with an auto-detector for both spacing and offset, which springs into action if you run the script with no selection.

The bottom part (or a similar one) might have a simple synthesisI set up a simple (clearly suboptimal) lls search which gave this result. There very likely better predecessors. In general I think that lls could help here a lot for those kind of problems.

Only slightly relates question: Is there a heurístic for guessing the number of gliders needed for a specific spaceship, e.g. depending on size, velocity and period? What are the major cost drivers (I sound like my budget controller )?

HartmutHolzwart wrote:Only slightly relates question: Is there a heurístic for guessing the number of gliders needed for a specific spaceship, e.g. depending on size, velocity and period? What are the major cost drivers (I sound like my budget controller ;-))?

Someone like Extrementhusiast or Kazyan would probably be better at answering this, so I'm just going to say a few random things and see if that provokes any disagreement from the experts.

How about "1-2 gliders per space dust cell"?I do have one rule of thumb that has actually worked (once) to produce a good advance estimate of number of gliders needed. It was based on the amount of "space dust" in the target object -- about a 40-cell region, similar to the area taken up by a 25P3H1V0.1 or maybe an Edge-repair spaceship 1. Based on glider recipes of these other known objects with about 40 cells of space dust, the estimate was 50-100 gliders, and the right number turned out to be 67.

Of course, that only works when objects with comparable size and structure are available (and maybe not even then). I'm not sure how the rule could best be adjusted to account for the 264-glider synthesis of a p6 pipsquirter, for example, which has less than 40 cells of space-dust rotor, but a big area of stator around it making the rotor less accessible. Probably it's safer to stick with spaceships for now, since they don't usually have a hard stable motionless crunchy outside and a squishy space-dust center.

Known Data Points...30P4H2V0.4 has 70 or 80 cells of space dust, depending on how you count, but maybe it should get a discount for having a couple of B-heptominoes at the front. Its cost is 85 gliders -- seems reasonable.'

46P4H1V0 maybe also gets a discount for a pair of leading traffic light predecessors. It has about 50 space dust cells per half, 100 for the whole spaceship... and possibly an additional minor discount for symmetry. That one is 99 gliders, which also seems in line with a gradual increase in cost based on amount of space dust.

... But Not Enough to Extrapolate FromWe really don't have enough data from these small spaceships to even make an educated guess about something the size of Sir Robin, which has something on the order of 600 cells of space dust. Even if the cost increase is roughly linear -- 1-2 gliders per space-dust cell -- we'd be looking at 1000+ gliders in a Sir Robin recipe. And I'm afraid the rule may be something more like "double the number of gliders every time you add 50 space-dust cells", which would give us a 100,000-glider estimate instead. (!)

Stable Stuff Is Good, ThoughI think maybe we _can_ say that slower spaceships are significantly easier to construct. Or maybe the right thing to say is that spaceships with stable chunks are much cheaper, and stable chunks are much more likely as the speed goes down. The loafer's loaf, the copperhead's trailing block, and the central spine of 60P5H2V0 all make those respective synthesis problems a lot easier. Compare 60P5H2V0 with 44P5H2V0, a "tough nut to crack" because there's nothing stable toward the middle to use as a starting point.

Period and velocity might not actually matter so much, except to the extent that higher period and slower speed help to enable stable centers.

Pretty much all the recent difficult syntheses have been done by finding stable objects or constellations that can be ignited by controlled explosions around the edges to make the target spaceship -- whether the final product actually has any stable stuff in it or not. That seems like a big hint for some specialized future version of lifesrc that searches for predecessors while maintaining an always-growing core of stability toward the center.